It is common practice in the wet cell storage battery art to provide plugs which are threaded, or otherwise fitted into the fill holes of present-day storage batteries. These plugs are vented so that gases developed within the battery, for example, during the charging operation, may escape. However, it is important that the corrosive liquid electrolyte within the battery does not leak out through the vents in the plugs, as such spillage has an adverse effect on surrounding surfaces and on personnel handling the batteries, as well as being wasteful of the electrolyte. This leakage problem is not too serious when the storage battery is operated in an upright position. However, there are many uses of storage batteries, such as in aircraft, water vessels, racing cars, and the like, in which the batteries are subject to violent action, to being tilted away from their normal upright position, and of actually being inverted for substantial periods of time. For such uses, it is common practice in the prior art to provide nonspill plugs having internal tiltresponsive valve mechanisms for the fill holes of the such batteries. Various types of nonspill plugs are known to the art, and are described, for example, in U.S. Pat. Nos. 2,306,974; 2,717,610; and 3,752,173.
As described, for example, in U.S. Pat. No. 3,752,173, one form of nonspill vent plug known to the art includes a tubular casing which, in turn, includes an inwardly projecting shoulder that divides the interior of the casing into an upper portion and a lower portion. A tiltable weight is positioned in the upper portion of the casing, and it is supported on the shoulder. A valve stem is secured to the tiltable bottom of the weight, the valve stem projecting downwardly through the lower portion of the casing and through an opening in the lower end of the casing. Whenever the axis of the prior art plug is tilted a predetermined angular distance away from the vertical, the weight tilts relative to the casing, and in so doing pulls the valve stem upwardly to close a valve supported on the lower end of the valve stem against a valve seat surrounding the opening in the lower end of the casing. This action seals the opening, thereby preventing electrolyte in the battery from leaking out through the plug when the battery is so tilted. It is also usual in such prior art plugs to provide a ball and socket joint between the tiltable weight and the valve stem, this being achieved by providing a cavity in the bottom of the weight which has a mating spherical surface with the ball at the top of the valve stem.
The principal objective of the present invention is to provide a closure assembly of the general type described in the preceding paragraph, but one which is constructed in an improved manner so that closure of the assembly is assured, without any likelihood of sticking, whenever the assembly is tilted beyond a predetermined angular threshold with respect to the vertical; and so as to assure that the closure assembly, at no time, will allow any liquid electrolyte to leak from the battery. The assembly of the invention is also constructed to be readily and economically manufactured, and to operate reliably over long periods of time.
Specifically, the main objectives of the present invention are to provide a closure assembly for wet cell storage batteries, which may be manufactured on a commercially feasible basis, and which operates to vent gases from the interior of the battery, and to provide a complete and positive closure when the battery is tilted even slightly from its upright position, and throughout all other positions of the battery, to minimize any leakage of liquid electrolyte from the battery.
In meeting the foregoing objectives, the closure assembly of the invention reduces the hazards which presently accompany the use of storage batteries, in that the corrosive electrolyte is maintained within the battery, despite violent movements of the battery, and short-circuiting electrical paths created by the escape of the electrolyte are also minimized. Moreover, the closure assembly of the invention serves to reduce the frequency with which fresh electrolyte and water must be added to the battery thereby reducing the maintenance requirements of the battery.
The closure assembly of the invention is actuated by a tiltable lead weight which is shaped in the form of a truncated cone, and which provides uniformity of valve closure for any attitude of the storage battery angularly displaced from the vertical beyond a predetermined threshold, this being achieved by maximizing the density of the lead weight and obviating the effect of imperfections or blow holes therein. The closure assembly of the invention also includes other features, such as a plstic disc which is attached to the lead weight, which forms a bearing surface for a ball joint within the assembly, and which assures accurate and reliable operation of the assembly whenever a tilt occurs beyond the presdetermined threshold. The closure assembly of the invention also includes a hydrophobic porous filter which acts as a secondary barrier to prevent any liquid from leaking through the closure under any condition.